1. Field of the Invention
This invention relates generally to safety equipment for use in conjunction with a loading dock, and specifically to a vehicle restraint to prevent accidental or unauthorized moving of a parked vehicle away from the dock while the vehicle is being loaded or unloaded.
2. Description of the Prior Art
Proper securing of a parked vehicle to a loading dock during loading or unloading is an essential safety precaution. When a securement system is not in place, the vehicle may accidentally or inadvertently be moved away from the dock. This in turn may result in serious injury to the dock personnel, as well as product damage or loss of the cargo being moved.
To prevent a parked vehicle from moving during such loading and unloading operations, a variety of vehicle restraints have previously been employed. In general, such restraints are mounted to the face of the loading dock, or the driveway approaching it, and include a hook or other retaining member which has a generally horizontally extending leg and a vertical projection and which restrains a vehicle bar suspended from the rear end of the parked vehicle. Typically, the vehicle restraint engages a horizontally disposed bar suspended from the rear of the vehicle as mandated by ICC regulations. Such a vehicle bar will be referred to herein as an ICC bar. An example of a vehicle restraint engaging a vehicle bar in the form of an ICC bar can be seen in U.S. Pat. No. 4,443,150 to Hahn, et al. the disclosure of which is incorporated herein by reference. In that type of vehicle restraint, the hook is carried within a vertically movable carriage. The carriage is biased upwardly and includes a sloping cam surface, which is engaged by the ICC bar as the truck backs into position to push the carriage downward from its elevated rest position. When the truck is fully backed in, the ICC bar is in engagement with a top surface of the carriage. The hook including the leg and vertical projection is then moved as a unit vertically from its rest position inside the carriage to its vehicle-engaging position wherein the ICC bar is captured behind the vertical projection of the hook.
Certain other restraints have used a pivotal hook movement wherein the retaining hook rotates from a stored position to a vehicle-engaging position such as in U.S. Pat. No. 4,264,259 to Hipp. That restraint has a movable carriage similar to that of the '150 patent, but the hook is pivotally mounted within the carriage. Pivotal movement of the hook places the vertical projection in a position where it can capture an ICC bar of a properly parked vehicle. The vehicle restraint of U.S. Pat. No. 4,759,678 to Hageman also shows pivotal movement of a hook housed within a carriage.
The types of restraints just described have used both manual and power-driven means for moving the hook. The '150 patent shows manual vertical movement of the entire hook, including the horizontal leg and the vertical projection. The '259 and '678 restraints both show pivotal movement of the hook by power-driven means which are external to the carriage. A further U.S. Pat. No. 4,472,099 to Hahn, shows a pivoting hook and a power-driven means housed within the carriage.
When the powered drive is external to the carriage, it may be subject to damage from the truck itself, or other external forces. Housing the powered drive in the carriage allows for protection from outside elements, but makes it susceptible to damage from uncontrolled movement of the hook or carriage. Further, housing of the powered drive for a horizontally-extending hook in the carriage limits the size of the drive since the hook itself requires space within the carriage--both for housing the hook and for allowing it unimpeded travel. As a result, the powered drive has less output capacity, and less ability to withstand excessive forces from uncontrolled movement of the hook or carriage, or from an attempt to move the vehicle while restrained. The problem of a low output capacity for the drive may be compounded by the fact that the horizontal leg and vertical projection of the hook make the hook relatively massive. Further still, a mounting of the powered drive in the carriage may require complex power-transfer mechanisms such as bar linkages and the like for moving the hook as in the '099 patent. This is particularly true in the case of a linearly moved horizontally-extending hook, since a vertical force must be applied to a member having a significant horizontal extent.
In the situation where the hook is moved manually, a significant force must be applied to move the hook including the relatively massive horizontal leg and vertical projection to its elevated vehicle-restraining position. Further, some means, such as a latch or other engaging mechanism, must be employed to maintain the entire hook including the horizontal leg and vertical projection in the elevated position. Thus, while these devices are effective in restraining a parked vehicle, they have certain shortcomings.